Sensing and mapping catheter for guiding and supporting balloon catheter

ABSTRACT

A catheter configured to guide and support a balloon catheter for use in and around a pulmonary vein and its ostium, has an elongated shaft and a distal assembly, the elongated shaft including a proximal portion with a first flexibility and a distal portion including a second flexibility greater than the first flexibility, the distal assembly including an elbow portion and a generally circular portion generally transverse to the longitudinal axis, the generally circular portion including a third flexibility greater than the second flexibility. Single axis location sensors and sensing ring electrodes are carried on the generally circular portion.

FIELD OF INVENTION

This invention relates to a catheter, in particular, anelectrophysiology catheter with location and electrical sensors.

BACKGROUND

Electrode catheters have been in common use in medical practice for manyyears. They are used to stimulate and map electrical activity in theheart and to ablate sites of aberrant electrical activity. Atrialfibrillation is a common sustained cardiac arrhythmia and a major causeof stroke. This condition is perpetuated by reentrant waveletspropagating in an abnormal atrial-tissue substrate. Various approacheshave been developed to interrupt wavelets, including surgical orcatheter-mediated atriotomy. Prior to treating the condition, one has tofirst determine the location of the wavelets. Various techniques havebeen proposed for making such a determination, including the use ofcatheters with a mapping assembly that is adapted to measure activitywithin a pulmonary vein, coronary sinus or other tubular structure aboutthe inner circumference of the structure. One such mapping assembly hasa distal “lasso” structure comprising a generally circular main regiongenerally transverse and distal to the catheter body, where the tubularstructure comprises a non-conductive cover over at least the main regionof the mapping assembly. A support member including shape-memory isdisposed within at least the circular main region of the mappingassembly. A plurality of electrode pairs, each comprising two ringelectrodes, are carried by the generally circular main region of themapping assembly.

More recently, balloon catheter have been put into use to ablatepulmonary vein ostia. A balloon with electrodes on its outer surface isadvanced into the left atrium where the balloon is inflated andpositioned to nest in an ostium for simultaneous circumferential tissuecontact around the ostium. However, depending on the size of the balloonand the ostium, the balloon can be dislodged from the ostium during anablation procedure.

Applicants recognized that there is a need to provide a catheter with adistal “lasso” assembly that can serve as a guidewire and support aballoon nesting in an ostium, while also being capable of sensingelectrical signals from tissue of a tubular region of the ostium andprovide location signals for 3-D mapping.

SUMMARY OF THE DISCLOSURE

In some embodiments, an electrophysiology catheter includes an elongatedshaft defining a longitudinal axis of the catheter, the shaft includinga proximal portion with a first flexibility and a distal portionincluding a second flexibility greater than the first flexibility; adistal assembly including an elbow portion and a generally circularportion generally transverse to the longitudinal axis, the generallycircular portion including a third flexibility greater than the secondflexibility; a single axis sensor situated in the generally circularportion; and a ring electrode situated on the generally circularportion.

In some embodiments, the elongated shaft includes a hypotube with alumen.

In some embodiments, the hypotube is coextensive with the proximalportion of the shaft.

In some embodiments, the catheter includes a preformed support memberwith shape memory that extends at least through the distal assembly,wherein a distal end of the preformed support member is received in thelumen of the hypotube.

In some embodiments, the catheter includes a preformed support memberwith shape memory that extends at least through the distal assembly.

In some embodiments, the preformed support member includes a proximalportion that extends through the shaft.

In some embodiments, the catheter includes a second support memberproximal of the preformed support member and extending through theshaft, the second support member including a distal end that is coupledto a proximal end of the preformed support member.

In some embodiments, the proximal portion of the shaft includes a firstdiameter D1, the distal portion of the shaft includes a second diameterD2, and the generally circular portion of the distal assembly includes athird diameter D3, and D1>D2>D3.

In some embodiments, the elbow portion of the distal assembly includes atransition portion whose proximal end is configured with the diameter D2and whose distal end is configured with the diameter D3.

In some embodiments, D1 ranges from about 0.030 inch to about 0.040inch, D2 ranges from about 0.018 to 0.011 inch, and D3 is about 0.011inch.

In some embodiments, an electrophysiology catheter includes an elongatedshaft defining a longitudinal axis of the catheter, the shaft includinga proximal portion with a first flexibility and a distal portionincluding a second flexibility greater than the first flexibility; adistal assembly including an elbow portion and a generally circularportion generally transverse to the longitudinal axis, the generallycircular portion including a third flexibility greater than the secondflexibility; a plurality of single axis sensors situated in thegenerally circular portion; and a plurality of ring electrodes situatedon the generally circular portion.

In some embodiments, the catheter includes an elongated support memberwith shape memory, the elongated support member being coextensive withthe distal portion of the shaft and with the distal assembly.

In some embodiments, the catheter includes a second support membercoextensive with the proximal portion of the shaft.

In some embodiments, the catheter includes a hypotube coextensive withthe proximal portion of the shaft.

In some embodiments, the elongated support member coextensive with theelbow portion of the distal assembly includes a transition portionhaving a distal end with a smaller diameter and a proximal end with alarger diameter.

In some embodiments, the transition portion tapers from the proximal endwith the larger diameter to the distal end with the smaller diameter.

In some embodiments, the proximal portion of the shaft has a firstlength and the distal portion of the shaft has a second length lesserthan the first length.

In some embodiments, the generally circular portion is configured forcircumferential contact with tissue in a tubular region.

In some embodiments, the support member includes a linear portionproximal of the generally circular portion configured to support aballoon of a second catheter for contact with an ostium of a pulmonaryvein.

In some embodiments, the support member includes a generally linearportion proximal of the generally circular portion, and the generallylinear portion is configured to support a balloon of a second catheterfor contact with an ostium of a pulmonary vein while the generallycircular portion is in circumferential contact with tissue in thepulmonary vein.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention will bebetter understood by reference to the following detailed descriptionwhen considered in conjunction with the accompanying drawings. It isunderstood that selected structures and features have not been shown incertain drawings so as to provide better viewing of the remainingstructures and features.

FIG. 1 is a perspective view of a catheter of the present disclosuresupporting a balloon catheter, according to one embodiment.

FIG. 2 is an end perspective view of an assembled preformed supportmember of a distal “lasso” assembly, according to one embodiment.

FIG. 3 is a side perspective view of a distal “lasso” assembly situatedin a pulmonary vein while supporting a balloon nested in an ostium ofthe pulmonary vein.

FIG. 4 is a side cross-sectional view of the distal assembly, includingan elbow section, according to one embodiment.

FIG. 5A is an end cross-sectional view of the distal assembly of FIG. 4,taken along line A-A.

FIG. 5B is an end cross-sectional view of the distal assembly of FIG. 4,taken along line B-B.

FIG. 6 is a side cross-sectional view of the distal assembly, includinga generally circular section, according to one embodiment.

FIG. 7 is a side cross-sectional view of a shaft, including a secondsupport member, according to one embodiment.

FIG. 8 is a side cross-sectional view of a shaft, including a hypotube,and of a distal assembly, according to another embodiment.

FIG. 9 is a side view of a hypotube, according to another embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following detailed description should be read with reference to thedrawings, in which like elements in different drawings are identicallynumbered. The drawings, which are not necessarily to scale, depictselected embodiments and are not intended to limit the scope of theinvention. The detailed description illustrates by way of example, notby way of limitation, the principles of the invention. This descriptionwill clearly enable one skilled in the art to make and use theinvention, and describes several embodiments, adaptations, variations,alternatives and uses of the invention, including what is presentlybelieved to be the best mode of carrying out the invention.

As used herein, the terms “about” or “approximately” for any numericalvalues or ranges indicate a suitable dimensional tolerance that allowsthe part or collection of components to function for its intendedpurpose as described herein. More specifically, “about” or“approximately” may refer to the range of values ±20% of the recitedvalue, e.g. “about 90%” may refer to the range of values from 71% to99%. In addition, as used herein, the terms “patient,” “host,” “user,”and “subject” refer to any human or animal subject and are not intendedto limit the systems or methods to human use, although use of thesubject invention in a human patient represents a preferred embodiment.

Referring to FIG. 1 and FIG. 2, embodiments disclosed herein include acatheter 10 that is configured for use with a balloon catheter 100,including an elongated support shaft 12 and a 3-D distal or “lasso”assembly 15. The distal assembly 15 carries one or more single axissensors (“SASes”) 13 configured to be responsive to external magneticfield generators (not shown) for generating signals representative oflocation of the distal assembly 15, as well as one or more ringelectrodes 11 configured sensing electrical signals from tissue. Thedistal assembly 15 includes a preformed support member 16 withshape-memory, e.g., a nitinol wire, which provides the 3-D or loopconfiguration of the distal assembly 15. In that regard, it isunderstood that describing the distal assembly 15 the shape-memoryelongated support member 16 includes portions that impart shape tocorresponding sections of the distal assembly 15, including a curvedportion 16C that corresponds with a curved section 15C of the distalassembly 15, and an elbow portion 16E proximal of the curved portion 16Cthat corresponds with an elbow section 15E of the distal assembly 15. Insome embodiments, the curved (e.g., circular, helical or loop, all termsused interchangeably herein) portion 16C of the support member 16 isgenerally transverse to the shaft 12 that defines a longitudinal axis Lof the catheter, and the curved portion 16C has a curved arc or lengththat spans at least 360 degrees, if not about 450 degrees with a distaloverlapping tail portion 16T. Moreover, the curved portion 16C isconfigured relative to the shaft 12 such that the longitudinal axis Ldefined by the shaft 12 intersects the curved portion 16C and is offsetfrom a center of a circle generally defined by curved portion 16C.

The elongated support shaft 12 of the catheter has a proximal section12P of lesser flexibility and a distal section 12D of greaterflexibility. The shaft 12 is configured to pass through a lumen of aballoon catheter 14 and aptly support the balloon 140 in an ostium 110of a pulmonary vein 130, as shown in FIG. 3, with the distal lassoassembly 15 extending into the pulmonary vein for circumferentialcontact with tubular tissue of the pulmonary vein. Advantageously, theproximal section 12P of the shaft is configured with sufficient rigidityto transmit axial pushability and torque imparted by a user, forexample, manipulating a connector handle 27 (FIG. 1) at a proximal endof the shaft 12 and a torquer 17 (FIG. 1) mounted on the proximalsection 12P, while the distal section 12D of the shaft is configuredwith sufficient flexibility to accommodate an indirect approach anglebetween the distal lasso assembly 15 and the ostium 110 in which thesupported balloon 140 sits.

In some embodiments, as shown in FIG. 1 and FIG. 2, the shape-memorysupport member 16 of the distal assembly 15 has an elongated form with asufficient length to extend through the entirety of the distal assembly15 and the shaft 12 combined. As such, the elongated support member 16includes the following:

-   -   (i) a longer, generally linear proximal portion 16P, with a        first diameter D1, that spans the length of the proximal section        12P of the shaft 12;    -   (ii) a shorter, generally linear distal portion 16D, with a        second diameter D2, that spans the length of the distal section        12D of the shaft 12;    -   (iii) a distal curved portion 16C, with a third diameter D3,        that spans the curved distal section 15C of the distal assembly        15; and    -   (iv) a relatively short elbow portion 16E, with a gradual        transitional diameter DT ranging from D2 to D3, that spans the        elbow section 15E, extending between the generally linear distal        portion 16D and the distal curved section 16C of the support        member 16;        where diameter D1>diameter D2>diameter D3 such that the proximal        portion 16P has the least flexibility, the distal portion 16D        has more flexibility and the distal curved portion 16C has the        greatest flexibility. In some embodiments, the diameter D1 is        about 0.030 inch, the diameter D2 ranges from about 0.014 inch        to 0.018 inch and the diameter D3 is about 0.011 inch. Between        the proximal portion 16P and the distal portion 16D, the        diameter of the wire 16 may have a step transition or a gradual        transition between the diameters D1 and D2, as needed or        appropriate. Between the distal portion 16D and the curved        portion 16C, the elbow portion 16E is configured with a gradual        transition between the diameters D2 and D3. In some embodiments,        the gradual transition between diameters D2 and D3 occurs in a        span of about 2 mm in the elbow portion 16E. The length of the        proximal portion 16P of the support member 16 is not critical.        However, in some embodiments, the length of the distal portion        16D is at least the longitudinal length of the balloon 140 so it        can accommodate the balloon when it is supporting the balloon.        In some embodiments, the length of the shaft 12 is about 2        meters, where the distal portion 12D (with the greater        flexibility relative to the proximal portion 12P) has a length        ranging between about 6 cm and 8 cm.

With reference to FIG. 2 and FIG. 4, the distal curved portion 16C ofthe shape-memory support member 16 carries one or more SASes. It isunderstood that each SAS 13 has a respective wire coil sensor 50 and acable 20, where the wire coil sensor 50 is wrapped around a selectedlocation on the distal curved portion 16C and the cable 20 includes adedicated pair of wires 21, 21′ that are encased along with shieldingfibers 23 within an insulating sheath 22 generally coextensive with thewires 21, 21′. For simplicity in the description provided herein, wires21, 21′ of all SASes 13 carried on the distal assembly 15 areillustrated herein as passing through one common insulating sheath 22with shared shielding fibers 23 in forming a single cable 20 for allSASes 13.

In the illustrated embodiment of FIG. 2, the distal assembly 15 carriesthree SASes, namely, proximal SAS 13A, middle SAS 13B and distal SAS13C, including three wire coils 50A, 50B and 50C, referred to hereinrespectively as the proximal coil, the mid coil and the distal coil,that are arranged in equi-angular positions about the curved portion16C, e.g., at about 0, 120 and 240 degrees. The wire coil 50 of each SASis connected to a dedicated pair of wires 21 and 21′, with the wire 21connected to a distal end of the wire coil 50 and the wire 21′ connectedto a proximal end of the wire coil 50. Thus, in the illustratedembodiment, the distal coil 50C (best shown in FIG. 6) is connected towire pair 21C and 21C′, the mid coil 50B is connected to wire pair 21Band 21B′ and the proximal coil 50A is connected to wire pair 21A and21A′. To assemble the SASes 13A, 13B and 13C on the curved portion 16Cof the preformed support member 16, a method making or assembling apreformed support member with SASes in some embodiments includes (i)wrapping the wire coil 50C on the preformed support member 16 atlocation 240 degrees to form SAS 13C, (ii) connecting the wire pair 21Cand 21C′ to the distal and proximal ends, respectively, of the wire coil50C, and (iii) wrapping the wire pair 21C and 21C′ around the curvedportion 16C in a proximal direction. Different wrapping patterns may beemployed to provide strain relief against wire breakage during use ofthe catheter.

The method of assembling also includes (iv) wrapping the wire pair 21Cand 21C′ at location 120 degrees, (v) wrapping the wire coil 50B overthe wrapped wire pair 21C and 21C′ to form SAS 13B, (vi) connecting thewire pair 21B and 21B′ to the distal and proximal ends, respectively, ofthe wire coil 50B, and (vi) wrapping the wire pairs 21C and 21C′ and 21Band 21B′ around the curved portion 16D in a proximal direction.

The method of assembling further includes (vii) wrapping the wire pairs21C and 21C′ and 21B and 21B′ at location 0 degrees, (viii) wrapping thewire coil 50A over the wrapped wire pairs 21C and 21C′ and 21B and 21B′to form SAS 13A, (ix) connecting the wire pair 21A and 21A′ to thedistal and proximal ends, respectively, of the wire coil 50A, and (x)wrapping the wire pairs 21C and 21C′, 21B and 21B′, and 21A and 21A′around the curved portion 16C in a proximal direction. It is understoodthat one or more heat shrink sleeves may be over the formed SASes andthe wrapped wire pairs between adjacent SASes.

It is also understood that the sequence of the actions recited above orthe direction of wrapping (e.g., distal to proximal or proximal todistal) may be varied, as desired or appropriate and that a heat shrinksleeve can be placed over each SAS, the wire coils or wrapped wirepair(s) beneath the wire coils, as desired or appropriate. In any case,the distal SAS 13C includes the wire coil 50C with its distal endconnected to the wire 21C and its proximal end connected to the wire21C′, the mid SAS 13B includes the wire coil 50B with its distal endconnected to the wire 21B and its proximal end connected to the wire21B′, where the wire coil 50B is coiled over the wires 21C and 21C′, andthe proximal SAS 13A includes the wire coil 50A with its distal endconnected to the wire 21A and its proximal end connected to the wire21A′, where the wire coil 50A is coiled over the wires 21C and 21C′ and21B and 21B′.

At the elbow portion 16E, the cable 20 housing the wire pairs 21 (e.g.,21A, 21A′, 21B, 21B′, 21C and 21C′) advantageously lies on an insidesurface 52 (inward facing toward the curvature) of the elbow portion 16Ein minimizing the outer diameter of the distal assembly 15 in thatregion, as better shown in FIG. 4, FIG. 5A and FIG. 5B. In that regard,the distal end of the insulating sheath 22 of the cable 20, and theshielding fibers 23 therein are cut or otherwise terminated proximal ofthe elbow portion 16E to expose the various wire pairs 21. Moreover, allof the wires 21 are spread or fanned out, laid against the insidesurface 52, and affixed by an adhesive 37 (FIG. 5B) to minimize thecircumferential size and profile of the distal assembly 15 at its elbowportion 15E. The distal end portions of the shield fibers 23 may bewrapped around the wires 21 and the preformed support member 16 (FIG. 4)to encircle them for a tighter profile around the preformed supportmember 16. A heat shrink sleeve 38 may extend over the cable 20 and theshielding fibers 23 proximal of the elbow portion 16E, and the exposedwires 21 and safety fibers 25 in the elbow portion 16E. Proximal andterminal ends of the heat shrink sleeve may be at any location along thesupport member 16, as needed or appropriate.

Accordingly, the method of assembling the preformed support member 16with the SASes, includes (i) preparing the cable 20 for affixation to anelbow portion 16E; and (ii) affixing the prepared cable to the elbowportion, wherein the preparing the cable includes: (a) cutting orterminating a distal end of the outer insulating sheath 22 generallyproximal of the elbow portion; (b) exposing the wires 21 in the cable;(c) spreading or fanning out the exposed wires 21, and wherein theaffixing the prepared cable includes: (a) laying the fanned out exposedwires onto an inside surface 52 of the elbow portion; (b) applyingadhesive to the fanned out exposed wires 21 on the inside surface of theelbow portion; and (c) covering the affixed exposed wires and at least adistal portion of the insulating sheath 22 with a heat shrink sleeve.The preparing the cable may also include cutting or terminating distalends of the shielding fibers 23, and wrapping the distal ends around theexposed wires 21 and the preformed support member 16. The affixing theprepared cable may also include covering a plurality of safety strands25 (e.g., VECTRAN strands) whose proximal ends are anchored to the shaft12 and whose lengths are coextensive with the wires 21 under the heatshrink sleeve 38 to tether the distal assembly 15 to the shaft 12 as asafety measure against detachment of the distal assembly 15. Distal endsof the safety strands 25 may be anchored to a distal end of thepreformed support member 16. A description of suitable SASes is providedin U.S. Pat. No. 8,792,962, the entire content of which is herebyincorporated by reference.

As previously mentioned, the distal assembly 15 not only carries one ormore SASes 13, it also carries one or more ring electrodes 11. As shownin FIG. 6, the distal assembly 15 includes an outer braided tubing 40that has the ring electrodes 11 and conductive lead wires 41. Althoughthe tubing 40 has a lumen 39, the conductive wires 41 are embedded inthe side wall 42 as part of an extrusion manufacturing process of thetubing 40, as understood by one or ordinary skill in the art. In someembodiments, the outer braided tubing 40 covers the entire length of thepreformed support structure 16, including the proximal portion 16P, thedistal portion 16D, the elbow portion 16E, and the curved portion 16C.Of the portion of the braided tubing 40 that covers the curved portion16C, the ring electrodes 11 carried thereon are formed by selectiveremoval, e.g., laser cutting, of the outer side wall 42 to form recesses44 at predetermined locations so as to expose selected individual wires41. Conductive epoxy 43, for example, platinum conductive epoxy or goldconductive epoxy, is then applied to fill the recesses 44 and also alongthe circumference at the recess around the exterior of the side wall 42to form a respective ring electrode 11 at each of the predeterminedlocations. Thus, a method of constructing an outer tubing 40 with ringelectrodes 11 and embedded lead wires 41 includes: (i) extruding atubing 40 with wires 41 embedded in side wall 42, where the tubing hasan exterior surface, and an interior surface defining a lumen; (ii)removing a portion of the side wall from the exterior surface to exposea wire 41 within a recess; (iii) applying conductive epoxy to fill therecess and a corresponding circumferential band around the recess toform a ring electrode 11. Extruding the tubing 40 with the wires 41 maybe accomplished with conventional wire extrusion machines. Braided wires41 embedded in the side wall 42 of the tubing 40 may extend distal oftheir respective ring electrodes without any adverse impact on thefunction of the ring electrodes.

After the outer tubing 40 has been constructed with the ring electrodes11 and the embedded wires 41, the outer tubing 40 can be slipped on overthe assembled distal assembly 15. In some embodiments, a method ofassembling includes: (i) the above-described method of making orconstructing the outer tubing 40 with the ring electrodes 11 andembedded wires 41; (ii) the above-described method of assembling thepreformed support member 16 with the SASes 13; and (iii) mounting theconstructed outer tubing 40 onto the preformed support member 16 withthe SASes 13. Mounting may be accomplished by inserting the assembledpreformed support member 16 into the lumen 39 of the constructed outertubing 40. As such, the construction of the catheter 10 is simplified bycompartmentalization into construction of the outer tubing 40 whichprovides the ring electrodes, and construction of the underlyingSAS-carrying support member 16. Distal ends of the outer tubing 40 andthe support structure 16 may be jointly plugged and sealed with a ballof sealant, e.g., polyurethane, to form an atraumatic bulbous distal endof the catheter 10.

At the proximal end of the outer tubing 40 terminating near or in theconnector handle 27, proximal portions of the wires 41 may be exposedfrom the tubing 40 by selective removal of the side wall 42 forconnection to suitable electrical terminals in the connector handle 27in the transmission of sensed electrical signals to an electrophysiologyworkstation for processing, as known in the art. The cable 20 (includingthe wire pairs 21, 21′ of each SAS carried on the distal assembly 15)extends through the lumen 39 of the outer tubing 40, coextensively withthe distal and proximal portions 16D and 16P of the support member 16,in passing through the shaft 12 of the catheter and into the connectorhandle 27 in the transmission of location signals to theelectrophysiology workstation for processing, as known in the art.

In alternate embodiments, a shorter support member 16 is without theproximal portion 16P and has a proximal end that terminates at asuitable location proximal of the distal portion 16D and the elbowportion 16E. As shown in FIG. 7, the shorter support member 16 has aproximal end 16PE at, for example, about 8.0 cm proximal of the elbowportion 16E and is connected via a lumened coupler 31 to a secondsupport member 30, e.g., a metal or stainless steel wire, that extendsproximally toward the connector handle 12, where the 8.0 cm is selectedon the basis of the longitudinal length of the balloon 140 that issupported on the distal linear portion 12D of the shaft 12 when thedistal assembly 15 is inside the tubular region 120 of the ostium 110 onwhich the distal surface of the balloon rests (FIG. 3). The outer tubing40 with the ring electrodes 11 and embedded wires 41 extends over thesupport member 16 and the second support member 30, so as to cover theentirety of the distal assembly 15 and the shaft 12. The SAS cable 20extends in the lumen 39 of the tubing 40 coextensively with the supportmember 16 in the distal shaft portion 12D and with the second supportmember 30 in the proximal shaft portion 12P, and may be outside of thecoupler 31. To provide the different flexibilities in the shaft 12 andthe distal assembly 15, the second support member 30 has the diameterD1, the distal portion 16D of the support member 16 has the diameter D2,and the curved portion 16C of the support member 16 has the diameter D3,where D1>D2>D3 such that the second support member 30 has the leastflexibility, the distal portion 16D has greater flexibility, and thecurved portion 16C has the most flexibility. Again, the elbow portion16E provides a gradual transition of diameter from D2 to D3, but theremay be a step transition between the diameters D1 of the second supportmember 30 and D2 of the distal portion 16D at the coupler 31.

In other alternate embodiments, as shown in FIG. 8, the shorter supportmember 16 (without the proximal portion 16P) has a proximal end that isreceived in a distal end of a lumened structure, e.g., a hypotube 16with lumen 28, that extends proximally toward the connector handle 27.The shorter support member 16 extends through an outer covering 32,e.g., of PELLETHANE, whose lumen 36 receives the SAS-carrying curvedportion 16C and the distal portion 16D, and whose proximal end 32P abutswith a distal end 18D of the hypotube 18. As understood by one ofordinary skill in the art, conductive bands 33 are mounted over theouter covering 32 to form the ring electrodes 11 on the distal assembly15. Lead wires 48 connected to respective conductive bands 33 pass intothe lumen 36 via through-holes 34 formed in side wall 35 of the outercovering 32. Inside the lumen 36, the lead wires 48, along with thecable 20 for the SASes in the distal assembly 15, extend proximally andpass through the lumen 28 of the hypotube 18 toward the connector handle27. In some embodiments, the hypotube 18 has an outer diameter rangingfrom about 0.030 inch to 0.040 inch. As shown in FIG. 9, a distalportion of the hyptube 18 may be configured with one or more spiral cuts45 to increase flexibility.

In use, the catheter 10 is fed into and through a lumen 120 of theballoon catheter 100, where the lumen 120 extends through a shaft 130 ofthe balloon catheter and the balloon 140 itself. To feed the distalassembly 15, it is straightened so that the curved portion 15C firstenters the lumen 120 followed by the elbow 15E, and so forth. The distalassembly 15 is advanced relative to the balloon catheter until thedistal assembly 15 passes the distal end of the balloon catheter, uponwhich the distal assembly 15 is free to assume the 3-D shape in thepatient's left atrium pursuant to its underlying preformed shape-memorysupport member 16. The catheter 10 is then maneuvered so as to insertthe distal assembly 15 into a pulmonary vein where the ring electrodes11 are in contact with tissue along an inner circumference of tubularregion of the pulmonary vein. Using the shaft 12 and particularly thedistal section 12D as a guidewire, the balloon catheter 100 is thenadvanced toward the ostium of the pulmonary vein until a distal surfaceof the balloon comes into contact with the ostium. The shaft 12 of thecatheter 10 has a less flexible proximal section 12P so as to functionas a guidewire for the balloon catheter 100 and a more flexible distalsection 12D so as to allow flexure where the approach angle of thedistal assembly 15 is not in alignment with the center of the ostium,yet have sufficient rigidity to aptly support the balloon thereon. Theone or more SASes 13 in the distal assembly 15 respond to externalmagnetic field generators typically located under the patient's bed toprovide location signals, and the ring electrodes 11 carried on thedistal assembly 15 sense electrical signals from the tissue of thepulmonary vein, including electrical signals to assess whether PVisolation has been achieved by ablation of tissue of or adjacent theostium.

The preceding description has been presented with reference to presentlypreferred embodiments of the invention. Workers skilled in the art andtechnology to which this invention pertains will appreciate thatalterations and changes in the described structure may be practicedwithout meaningfully departing from the principal, spirit and scope ofthis invention. Any feature or structure disclosed in one embodiment maybe incorporated in lieu of or in addition to other features of any otherembodiments, as needed or appropriate. It is understood that a featureof the present invention is applicable to multiplying linear motion of apuller wire, contraction wire, or any other object requiring insertion,removal, or tensioning within a medical device, including the disclosedelectrophysiology catheter. As understood by one of ordinary skill inthe art, the drawings are not necessarily to scale. Accordingly, theforegoing description should not be read as pertaining only to theprecise structures described and illustrated in the accompanyingdrawings, but rather should be read consistent with and as support tothe following claims which are to have their fullest and fair scope.

What is claimed is:
 1. An electrophysiology catheter, comprising: anelongated shaft defining a longitudinal axis of the catheter, the shaftincluding a proximal portion with a first flexibility and a distalportion including a second flexibility greater than the firstflexibility; a distal assembly including an elbow portion and agenerally circular portion generally transverse to the longitudinalaxis, the generally circular portion including a third flexibilitygreater than the second flexibility; a single axis sensor situated inthe generally circular portion; and a ring electrode situated on thegenerally circular portion.
 2. The catheter of claim 1, wherein theelongated shaft includes a hypotube with a lumen.
 3. The catheter ofclaim 2, wherein the hypotube is coextensive with the proximal portionof the shaft.
 4. The catheter of claim 3, further including a preformedsupport member with shape memory that extends at least through thedistal assembly, wherein a distal end of the preformed support member isreceived in the lumen of the hypotube.
 5. The catheter of claim 1,further including a preformed support member with shape memory thatextends at least through the distal assembly.
 6. The catheter of claim5, wherein the preformed support member includes a proximal portion thatextends through the shaft.
 7. The catheter of claim 5, further includinga second support member proximal of the preformed support member andextending through the shaft, the second support member including adistal end that is coupled to a proximal end of the preformed supportmember.
 8. The catheter of claim 1, wherein the proximal portion of theshaft includes a first diameter D1, the distal portion of the shaftincludes a second diameter D2, and the generally circular portion of thedistal assembly includes a third diameter D3, and D1>D2>D3.
 9. Thecatheter of claim 8, wherein the elbow portion of the distal assemblyincludes a transition portion whose proximal end is configured with thediameter D2 and whose distal end is configured with the diameter D3. 10.The catheter of claim 8, wherein D1 ranges from about 0.030 inch toabout 0.040 inch, D2 ranges from about 0.018 to 0.011 inch, and D3 isabout 0.011 inch.
 11. An electrophysiology catheter, comprising: anelongated shaft defining a longitudinal axis of the catheter, the shaftincluding a proximal portion with a first flexibility and a distalportion including a second flexibility greater than the firstflexibility; a distal assembly including an elbow portion and agenerally circular portion generally transverse to the longitudinalaxis, the generally circular portion including a third flexibilitygreater than the second flexibility; a plurality of single axis sensorssituated in the generally circular portion; and a plurality of ringelectrodes situated on the generally circular portion.
 12. The catheterof claim 11, further comprising an elongated support member with shapememory, the elongated support member being coextensive with the distalportion of the shaft and with the distal assembly.
 13. The catheter ofclaim 11, further comprising a second support member coextensive withthe proximal portion of the shaft.
 14. The catheter of claim 11, furthercomprising a hypotube coextensive with the proximal portion of theshaft.
 15. The catheter of claim 12, wherein the elongated supportmember coextensive with the elbow portion of the distal assemblyincludes a transition portion having a distal end with a smallerdiameter and a proximal end with a larger diameter.
 16. The catheter ofclaim 15, wherein the transition portion tapers from the proximal endwith the larger diameter to the distal end with the smaller diameter.17. The catheter of claim 11, wherein the proximal portion of the shafthas a first length and the distal portion of the shaft has a secondlength lesser than the first length.
 18. The catheter of claim 11,wherein the generally circular portion is configured for circumferentialcontact with tissue in a tubular region.
 19. The catheter of claim 11,wherein the support member includes a linear portion proximal of thegenerally circular portion configured to support a balloon of a secondcatheter for contact with an ostium of a pulmonary vein.
 20. Thecatheter of claim 11, wherein the support member includes a generallylinear portion proximal of the generally circular portion and thegenerally linear portion is configured to support a balloon of a secondcatheter for contact with an ostium of a pulmonary vein while thegenerally circular portion is in circumferential contact with tissue inthe pulmonary vein.